Supposed Marijuana And Schizophrenia Link “Overstated”

[Editor’s note: This post is excerpted from this week’s forthcoming NORML weekly media advisory. To have NORML’s media advisories delivered straight to your in-box, sign up for NORML’s free e-zine here.] Clinical evidence indicating that marijuana use may be casually linked to incidences of schizophrenia or other psychological harms is not compelling, according to a scientific review published online by the journal Addiction.
Investigators at the University of Bristol, Department of Social Medicine assessed the potential health risks of cannabis, particularly whether use of the drug may be causally linked with mental illness.
Authors wrote: “We continue to take the view that the evidence that cannabis use causes schizophrenia is neither very new, nor by normal criteria, particularly compelling. … For example, our recent modeling suggests that we would need to prevent between 3000 and 5000 cases of heavy cannabis use among young men and women to prevent one case of schizophrenia, and that four or five times more young people would need to avoid light cannabis use to prevent a single schizophrenia case. … We conclude that the strongest evidence of a possible causal relation between cannabis use and schizophrenia emerged more than 20 years ago and that the strength of more recent evidence may have been overstated.
In 2007, an analysis in the British medical journal The Lancet estimated that experimenting with marijuana could increase one’s risk of developing a psychotic illness later in life by some 40 percent. Following this report, Parliament in 2008 voted to reclassify marijuana as a Class B substance, making its possession punishable by up to five years in prison.
University of Bristol researchers also criticized Parliament’s reclassification of the drug, which took effect earlier this year. They concluded: “The only important possible benefit of prohibition is prevention of cannabis use. There is little or no evidence that it effectively achieves this benefit. Patterns of cannabis use in the population appear to be independent of the policy surrounding use, and criminalizing individual cannabis users does not appear to modify their use in a healthy way.
Overall, investigators determined that marijuana’s most significant health risk was its association and reinforcement with tobacco smoking.

0 thoughts

  1. If cannabis made you go psycho, we’d see that represented in the general population, and we don’t see that. A large percentage of the population consume cannabis on a regular basis, just as people use coffee, energy drinks and such every day.
    To watch great videos on the reality of the current cannabis industry, or to share with friends and family, check out or

  2. It’s tough to get straight scientific answers sometimes when it comes to cannabis, due to its (inappropriately) political nature.
    From a health perspective, though, it makes sense that hybrid cannabis may not be optimal, particularly as created via man’s ego-dominated mind state. (And in fact the ego-dominated state looks to re-enforce its own insanity in its creations.)
    I’m the first to admit that the thought of “the ultimate” or “what’s the new thing” is appealing…but perhaps the movement away from cannabis’ natural chemical balances is NOT optimal for human health. This statement would apply to any plant that’s been hybridized.
    I would love to see cannabis treated more like “just another plant” so its study can be focused on instead of political back-and-forth ideologizing.

  3. please nothing is going to happen especially since so many americans in power actually want to curb our freedoms not expand them which is why cannabis legalization will never happen unless we advocated for legalization escalate this movement
    when those in power harm and hurt so many of its citizens its time we pay back these organizations in kind
    the govt is regulating and criminalizing things they have no right. they delve in to millions of lives in the fact that those in govt believe that gays shouldnt get married, this is the same with cannabis regulation, who are they to say what people do with their personal lives, and the choices they make especially when it holds no consequences to anyone.
    the govt has no right to regulate the free will of the people

  4. So.. this article is very sketchy and i wondering if someone could explain whether it does or doesn’t cause Schizophrenia ?

  5. Has anyone thought that maybe the reason that marijuana would be associated with schizophrenia is because some schizophrenics were smoking in order to get some relief from their symptoms? Some may have misunderstood the relationship there, and assumed that the marijuana was making the people schizophrenic. There must be some unbiased clinical trial somewhere, with certified non-schizophrenics smoking out and seeing if they develop the psychosis. Now to be perfectly fair, most crime is committed by “sane” people, so if this is a tactic to scare us away from legalization, “Don’t legalize or the crazies will get you,” it can be safely ignored.

  6. What truly surprises me is this: Unless a person is a proactive supporter of cannabis, they don’t ask questions. They take people’s words for it. There are a series of questions which always need to be asked. Among that list: What prior, non-marijuana-related tendencies or underlying issues might these particular people have had prior to being diagnosed with schizophrenia? Describe in specific detail what, at minimum, entails schizophrenia and what those so diagnosed exhibited relative to schizophrenia symptoms. Was the study highly controlled? What was the prior mindset and setting of the schizophrenics before they were ill? Were the people studied carefully chosen (which can be done to alter results) or picked at random? Is there truly a causal link with cannabis? (Apparently not) Is cannabis attributable on any level to schizophrenia or is it possible that these were (again) carefully chosen people or just a lucky batch of schizophrenics (Unlucky for them, really) who happened to have at one point consumed cannabis? In either case, is it not possible for such a ‘link’ to be chance? The list goes on. Also, the percentages are weird. If schizophrenia is likely to increase 40%, is that only while high (altered states of mind, no matter how healthy, will not fit into what is psychologically [and arbitrarily] known as sane) or is that permanent? Also (And this is where it comes apart and shows it for the confusing mess it is to begin with), just what the hell were my imaginary chances of succumbing to schizophrenia before consumption. Clearly, there’s and ‘after’ percentage so there must be a ‘before’ percentage. One person could already have a 80% chance of developing schizophrenia prior to consuming cannabis. Whatever imaginary number one applies to percentage increase, post-consumption, that 80%-er is going to wind up in a mental institution somewhere down the line.

  7. weed will only enhance these existing problem in some people and make them aware of these preexisting mental scars most of these study s were done with opinions from drug users that used multiple drugs and medications through out life i will name at-least 10 mental medications that caused me and will cause permanent
    mental issues like schizophrenia one of my all time worse drugs ever made seroquel will leave a good engraving in your cardio and brain system neutontin will cause u tripple the nerve damage than smoking crack 5 years effexor will give some one permanent schizophrenia and long term sleep disorders permanate nerve damage as well as anixiaty disorders
    the list goes on fromn zyprexa zoloft riddlin jeeze u give your kid riddling you might as well teash em how to make crack im sick of the medication company’s lying to people but i do know that earned their spot in hell already its murder so is the marijuana law its murdered millions of people time n time again the law the road block to a persons future destroyed over a few hundred dollars and medical companies make that off some one single persons days fix of man made garbage that is only guarnteed to have them come back to the dr in the future for a different medicine needed to fix the problems left from the first one first medicine
    picture that your kids taking these antidepressants and it will develop into
    a bigger dose then a bigger dose then an additional prescription try 200 to 2000 a month to be normal the us government can fuck off for letting this go on so long thats why the usa is broke

  8. “We continue to take the view that the evidence that cannabis use causes schizophrenia is neither very new, nor by normal criteria, particularly compelling.” No their not trying to make people hysterical. Trying to mess with minds before they make the choice for themselves. Thanks to Reefer Madness and die hard prohibs, theirs no wonder why this would be said. 1% of the worlds entire population is believed to have some form of schizophrenia. 1%. All of a sudden their are more cases? I’m sure that only cannabis consumption causes a heightened chance of developing schizophrenia in later years. BS! So many determining factors play into the development of schizophrenia.
    “We conclude that the strongest evidence of a possible causal relation between cannabis use and schizophrenia emerged more than 20 years ago and that the strength of more recent evidence may have been overstated.” Gee, ya think? Casual relation/overstated? I guess that works in order to keep the people in check for a while. Casual relation is the term for we don’t quite know if their is or isn’t a direct correlation.
    “In 2007, an analysis in the British medical journal The Lancet estimated that experimenting with marijuana could increase one’s risk of developing a psychotic illness later in life by some 40 percent. Following this report, Parliament in 2008 voted to reclassify marijuana as a Class B substance, making its possession punishable by up to five years in prison.” Can anyone tell me how this helps those who are supposedly suffering from cannabis? I want to know exactly how they performed the experiment. I was unaware that they conducted such experiments in the UK considering it is illegal and frowned upon there as well. Think about it. 70 years now all of a sudden we’re hearing all this BS about cannabis. 70 years! Cannabis is bad? That might have worked for this long but it’s not good enough anymore. That’s cause they know it’s going to take more initiative/pressure on their part to keep cannabis where it is at currently.
    “Overall, investigators determined that marijuana’s most significant health risk was its association and reinforcement with tobacco smoking.” Keyword smoking. Tobacco is legal and it kills far more people than cannabis ever will. I’m not that surprised and it’s always a real treat when I see more of these findings and to think that they don’t find anything wrong with drugs that are legal and far more toxic. Leaves one to think who do these people work for and why they don’t care about the truth? All I want is the truth.

  9. it’s a shame that factual information doesn’t spread as easily as bunk science or government propaganda.

  10. causes it…..jesus, ill tell you, i feel that cannabis use has been a benefit for issues i have had for years in that area of schizophrenia. i find i can consentrate to finish arranging thoughts and getting important things of the day done.and, instead of lookin like a pile of laundry throwed on the couch, i am motavated to do what needs done and enlightenes me concerning projects being, work or allows comfort and peace to a vertually ,self destructive one…will ..EVER… tell me that cannabis is not a benefit for the millions of folks with mental or even emotional issues… the people who are scanning this site for information about the effects of cannabis……..ask those of us who use it…not a government led story about pumpin 100 times a normal dose in a rat to study the effects…..ask people who consume it and you will have learned the truth…

  11. “Overall, investigators determined that marijuana’s most significant health risk was its association and reinforcement with tobacco smoking.”
    Sounds like it would be a better statement to say that smoking tobacco is the leading cause of mental illness and not Cannabis. Could explain the nut cases I know that smoke cigs. Until it is legal at a federal level we will be ignorant of the truth.

  12. -Overall, investigators determined that marijuana’s most significant health risk was its association and reinforcement with tobacco smoking.
    That last statement gave me kind of a spooky feeling. Because the other night, I was contemplating the stupid absurdity in which we call cannabis prohibition, and the idiocy in our land concerning the government’s disdain for it’s reform. I couldn’t stop thinking, as I lit up my umpteenth Marlboro, that their desire for us to stop tobacco use is one of the main hindrances to our cause. I mean, let’s face it. If you are a cigarette user, you know as well as anyone else, that being high usually equates to cigarette consumption rising dramatically. I usually smoke about a pack to a pack and a half a day. When I’m high, I’ll kill sometimes two packs. I think it’s the same as cigarettes going very well with coffee or beer.

  13. Well folks,Ive suffered from the symptoms of schizophrenia all my life.And after using cannabis I feel much better.Alot less time is spent in hospital and using cannabis is much better then all the pills I’ve been on.Cannabis,no side effects,unless you consider euforia a side effect.And it’s time we face it, euforia to a schizophrenic mind is a God send.If you have time it is amazing what is on the net.Like going through this website I read a report saying that it’s possible people who suffer from schizophrenia have a problem with thier cannabinoid recepters CB1-CB2 and it’s possible that marijuana helps.
    Just my 2 cents

  14. In my experience, people with psychological issues are more likely to seek marijuana out for self-medication. Not the other way around.

  15. This is not new, every month or so new studies are being published about it. How about they study behavior habits due to prohibition and the only reason why some people ‘freak out’ is due to the extreme laws against it. Simply put, people freak out after smoking because they realized they just broke the law.

  16. The government can say what they want. It doesn’t matter. We have the internet now. They can’t stop us from finding out the truth. They can’t stop us from having these thoughts or smoking our weed. F*** the government.

  17. Cannabis prohibition has almost nothing to do with the minimal harm associated with consuming the flowering tops of a common shrub. Cannabis prohibition is all about some people controlling others. If I control what you consume, you are my slave. If you allow me to control what you consume, you are my willing slave. In either case, I own you. This is all well and good, unless you have a problem with being aslave. The fact is that cannabis consumption makes people think, and that scares the hell out of those intent on enslaving others. They want you to only think what they want, or not at all, the result of truely harmful alcohol consumption they promote.

  18. I am a Safety and Health Professional. Why do they let corporations expose their employees to industrial solvents but they won’t let people buy an organic herb that is safer than alcohol someplace other than a dark gun-and-knife-filled alley? They tell us they are protecting us from ourselves, but they don’t do much to stop corporations from poisoning the air and the groundwater. They aren’t doing the only sensible thing that would put an end to stray bullets in drive by shootings, change the law already! The attraction to prohibition fueled profitability is irresistible. The harsher the penalty the more a drug dealer can charge for a smaller amount. Washington State I-1068

  19. These are the possible side effects of the FDA approved LEGAL DRUGS, ASPIRIN/CAFFEINE:
    Dizziness; heartburn; irritability; nausea; nervousness; upset stomach.
    Severe allergic reactions (rash; hives; itching; difficulty breathing; tightness in the chest; swelling of the mouth, face, lips, or tongue); black or bloody stools; confusion; diarrhea; drowsiness; hearing loss; ringing in the ears; severe or persistent dizziness; severe or persistent stomach pain or heartburn; shakiness; trouble sleeping; vomiting.Hmmmm,and the side effects of Cannabis are relaxation and what?

  20. Just a quick off topic question. Has Norml or any of their followers heard about Ebay removing any copies of the magazine High Times? Not sure what would cause that, other than the fact Ebay’s former CEO is going to run for the office of Governor of California. She is “absolutley 100% against the legalization of marijuana, including medical marijuana”. Not sure if that has become main stream news yet. Just wondering if anyone has heard about it.

  21. “it’s a shame that factual information doesn’t spread as easily as bunk science or government propaganda.”
    One of my cries has been that the propaganda has been effective. Seemingly intelligent people still won’t listen to that sentence repeatedly coming out of my mouth. I’ve even said, “you don’t trust the government, why would you trust what they’ve said about cannabis?” Usually it’s the stupid deer in the headlights look and I know it’s time to move on.
    Cory #18, the schizophrenia link lies is a big one and needs to be debunked. If you’d care to (barf) go to pharmaceutical web sites you’ll read many articles on how cannabis makes a person go crazy and how it negatively affects the brain.

  22. I don’t believe these biased studies. I have seen far too many of these things to put any truth to them. Isn’t it funny that the government funded studies that show merit get swept under the rug while these flaky claims get the media attention? The real fact is that millions of people use this plant anyway whether or not the government says it is legal. There is a huge industry built upon keeping it illegal and they are not going down without a fight. I take prescription pain killers because I need them, even though there are side effects. Even over the counter pain killers have side effects. My experiences with cannabis over the past 35 years have shown me first hand that the only really dangerous side effect is getting caught with it.

  23. Here’s one link for you Cory.
    Recently I said good bye to two friends who, by my best efforts, would not listen to reason.
    This was the last and latest from an ex friend in Tennessee:
    “All this stuff does is kill the centers of the brain that are causing the pain. Its addictive too Lea… but if you want to go around stoned then do it honey. If they make it legal then I wont say crap.
    I can cite hundred of studies that say that if you do this then your health will deteriorate and you could develop cancer very quickly as a side kicker. Note para 2… about being sick all the time”.
    I tried once more to talk to this friend and when he said dopers that was the last straw for me.
    NORML: If I were a millionaire you’d have all the money you need. So sorry I’m not. Love you.

  24. The way i look at it, going on 39 years of tokin my mind should be on the DARK SIDE OF THE MOON by now and the rest of it beyond Pluto.

  25. Oh, come on now! This is NOT new information.
    As far back as the Report of the Indian Hemp Commission (1845???), people who made a serious study of the matter said that although cannabis was associated with psychological problems, the evidence showed that it was not that cannabis use caused the problems. Instead, people with these problems tried cannabis because it held hope of dealing with the problems, and in many cases continued use because it turned out that in their individual cases, it WAS effective in doing so.
    “Post hoc” ain’t always “propter hoc”!

  26. in feb of last year, my job of thirty two years decided to start drug testing. i have consumed cannabis longer then my time there. i have always felt reasonably healthy through the years but,this past year…..lets just say, is the worst i have felt in my entire life physically as well as emotionally. cannabis has been good to me all these years.i have used it in a conservative manner. i never had any lung issues or any lack of motivation issues like i do now…..dammit.

  27. I am the caregiver for the use of medical marijuana for my nephew who was diagnosed with severe Schizophrenia when he was 20 years old. I have never been a user and was very skeptical when my nephew came to live with me and told me that marijuana helped him by relieving his night terrors and making the voices that he heard in his head less prominent. At the beginning of his stay I insisted that he not use marijuana while living in my home and he complied. However, within a weeks time he was waking three to four times in the middle of the night yelling at the top of his lungs and talking to persons only he could see and hear. When he is hearing voices he has no volume control. It only took me three days of dealing with these issues before I began the process of becoming his caregiver so that he could use marijuana legally. My nephew is now 31 years old and no longer hears voices. He holds a job and when speaking with him one would never guess that he has schizophrenia. I’m not sure who creates the results of the so called studies that state that marijuana causes schizophrenia, but my suggestion to them is to live with someone that is inflicted with this terrible illness and then see if they are willing to watch the person suffer or will try using a substance that is not only natural but extremely helpful. Such is the case of medical marijuana and my nephew. When he came to me he was on 7 different medications, many of them narcotic based including high dosages of vicodin for pain and seroquel to make him sleep which causes the following side effects liver or kidney damage;
    heart disease, high blood pressure, heart rhythm problems; heart attack or stroke; low white blood cell (WBC) counts; thyroid disorder; seizures or trouble swallowing. He no longer uses any of his old medications with the exception of an injection of Halperidol IM once a month, which he has been taking since he was originally diagnosed…and his medical marijuana. He smokes it in the evenings before bed and sleeps all the way through the night and ingests it for pain in the form of baked goods or candy when needed. I cannot say enough about the virtues of this incredible plant. I still do not use it myself, but then I have never felt the need. However, I will say this, if ever I do need anything stronger than ibuprophen for pain marijuana will be the first thing I try. It works…I’ve seen it. Even for a schizophrenic.

  28. This means only one thing: we need to have federal bans lifted so we can learn the true dangers of pot’s effects on growing kids’ brains. That is of course, assuming they exist.

  29. I saw a recent television special that suggested that normal people do not become schizophrenic from marijuana use, but that a small subgroup of people with a certain genetic mutation are very likely to become schizophrenic from marijuana use, thereby skewing the results when applied to the population as a whole.

  30. i told my grandson that i smoked since 1974 and he goes who that has befor he was i feel old .wait a moment’i am old i hit53 in january.i was smoking reefer almost 36 years i dont drink i never learnd too do it right.the news is going to tell me that smoking picked up for people 55 too 59.some of us never stopped.

  31. Deborah #34 – I fully concur. I am the mother/carer of a 26 year old son who has suffered from schizophrenia for 5 years. He takes prescribed medication but also smokes marijuana daily. It improves his mood and calms his jangled nerves. He says it makes him feel “normal” for a while. He also smokes cigarettes heavily but that is typical of schizophrenia sufferers I believe. Unfortunately, a bad cough seems to be a side-effect, probably a combination of ciggies and the bong. He now doesn’t drink as much alcohol which is better for his health. The only thing I don’t like is the smell of his bong, it stinks his room out.

  32. Good morning all. I know that we need to have this as a medication. I know it alleviates many pains and after affects. I know this to be true because my Doctor prescribed it to me yet it is still illegal here in New York. I know I am breaking the law but there is no law I will follow that will kill me I am sorry I have a10 year old daughter I have to be here. Please free this finally especially for those who are sick and dying. I being one of them.

  33. I have smoked for 15 years and schizophrenia runs in my family. I often wonder if it keeps me from developing this major brain disorder not if it is liable to cause me to develop it.
    This study clearly needs to reconducted.

  34. I been around cannabis for overy 44 years and i have seen it efeat some oerson in a bad way if you have a memtl condition it agervats it if you have not been didoes if a problen it will shjow up my the cannabis forceing it. So since we know that the reasearchers cude use cannabis o study mentl elmes bef or it pops up in a person. the cannabis does not it self make a perason o nuts but it just agrefst it

  35. On one hand, there are a number of studies that conclude Marijuana dramatically increases one’s risk of developing schizophrenia. However, this seems to conflict with studies done in the last twenty years that show the incidence of schizophrenia across the world has been declining since 1960, a time after which marijuana use exploded. These studies conflict greatly, and more research needs to be done comparing the two.

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